Bacterial strains and plasmids.

a<p>Tc^r, tetracycline resistance; Ap^r, ampicillin resistance.</p>b<p>The amino acid substitutions in the ArmZ products produced by the indicated <i>armZ</i> mutant strains are highlighted in parentheses.</p>c<p>The amino acid substitutions in the mutant ArmZ products encoded by the indicated plasmids are highlighted in parentheses. WT, wild type.